Britannica Sources used in this answer

How do scientists measure ocean heat content?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Grinnell Glacier shrinkage — Global warming A series of photographs of the Grinnell Glacier taken from the summit of Mount Gould in Glacier National Park, Montana, in (from left) 1938, 1981, 1998, and 2006. In 1938 the Grinnell Glacier filled the entire area at the bottom of the image. By 2006 it had largely disappeared from this view.

Scientists measure ocean heat content (OHC)—the change in thermal energy within a specific volume of water—by integrating data from various in situ and remote sensing instruments.1

In Situ Measurements

Researchers collect direct temperature data from the air-water interface down to selected depths using:
* Floating sensors: Devices such as Argo floats drift through the ocean to record temperature profiles.12
* Ship-based instruments: Oceanographers use specialized equipment, including bathythermographs and expendable bathythermographs (XBTs), to obtain temperature records at various depths.3
* Aircraft-deployed probes: Sensors can be dropped from aircraft to measure sea surface temperatures and subsurface profiles.12

Remote Sensing and Validation

To provide a global perspective, scientists use satellite-borne radar altimeters to track changes in sea surface height. Because water undergoes thermal expansion as it warms, these height variations serve as proxies to estimate OHC. These satellite-derived values are used to check and validate the integrated in situ data, ensuring a more accurate assessment of the heat stored in the top 2,000 meters of the global ocean.12